Field of the Invention
The present invention relates to a breather device.
Description of the Related Art
A case for the transmission or the like of a vehicle is provided with a breather device that performs ventilation in the case. As such a breather device, there is a separate-type breather device in which a small box (breather box) with a small hole (breath port) for intake is placed as a separate member outside a case, and the interior of the case communicates with the interior of the box and thus communicates with the atmosphere via the small hole for intake.
If the temperature in the case rises along with the traveling of the vehicle, the pressure of air in the case is raised by cubical expansion. In this case, the air whose pressure has risen in the case flows into the box. The air that has flowed into the box is exhausted from the breath port to the atmosphere. On the other hand, if the pressure in the case lowers, external air is sucked from the breath port into the box.
Depending on the traveling state of the vehicle, water may enter the box via the breath port. Then, a gas containing mist-shaped water may exist in the box. Japanese Patent No. 5378487 proposes a technique of separating water from air in the box and suppressing water invasion into the case.
Although the technique described in Japanese Patent No. 5378487 can suppress water invasion into the case, air that has flowed from the case into the box is exhausted to the atmosphere. The air that has flowed from the case into the box may contain mist-shaped oil in the case. The mist-shaped oil is preferably returned to the case again. Even if not the mist-shaped oil but liquid oil flows from the case to the box, the oil in the box is preferably returned to the case again without being mixed with water.
Hence, the present invention enables returning of oil in a case, which has flowed into a breather device, to the case again.